Multi Array使用键合并到新数组中

Question

原始阵列：

$cat = Array ( 
    [0] => Array ( [id] => 2 [name] => W [pid] => 1 ) 
    [1] => Array ( [id] => 4 [name] => M [pid] => 1 ) 
    [2] => Array ( [id] => 5 [name] => C [pid] => 1 ) 
    [3] => Array ( [id] => 8 [name] => K [pid] => 7 ) 
    [4] => Array ( [id] => 9 [name] => B [pid] => 7 ) 
    [5] => Array ( [id] => 12 [name] => X [pid] => 11 )
)

我想得到这样的结果：

$cat = Array ( 
    [0] => Array (
        [pid]=>1,
        [item] => Array(
            [0] => Array ( [id] => 2 [name] => W ),
            [1] => Array ( [id] => 4 [name] => M ),
            [2] => Array ( [id] => 5 [name] => C )
        )
    ),
    [1] => Array (
        [pid]=>7,
        [item]=>Array(
            [0] => Array ( [id] => 8 [name] => K ),
            [0] => Array ( [id] => 9 [name] => B )
        )
    ),
    [2] => Array (
        [pid]=>11,
        [item]=>Array(
            [0] => Array ( [id] => 12 [name] => X )
        )
    )
)

如何？

Answer 1

$newCat = array();
array_walk($cat, function($v) use(&$newCat){
    $i = $v['pid']; 
    unset($v['pid']);
    if(!isset($newCat[$i]))
        $newCat[$i] = array('pid' => $i, 'item' => array());
    $newCat[$i]['item'][] = $v;
});

print_r( array_values($newCat) );

demo